1. Technical Field
The present invention relates, in general, to data processing systems and in particular to data storage devices within a data processing system. More particularly, the present invention relates to problems associated with elevated temperatures within data storage devices, including high density hard disk drives.
2. Description of the Related Art
The need for higher density hard disk drives has been increasing every year. Development of magnetoresistive (MR) sensors (also referred to as heads) for disk drives in the early 1990's allowed disk drive products to offer a maximum storage capacity with a minimum number of components (heads and disks). Fewer components mean lower storage costs, higher reliability and lower power requirements.
MR sensors are used to read magnetically encoded information from a magnetic medium by detecting magnetic flux stored in the magnetic medium. During operation, sense current is passed through the MR element of the sensor, causing a voltage drop. The magnitude of the voltage drop is a function of the resistance of the MR element. Resistance of the MR element varies in the presence of a magnetic field. As the magnitude of the magnetic field flux passing through the MR element varies, the voltage across the MR element also varies. Differences in the magnitude of the magnetic flux entering the MR sensor can be detected by monitoring the voltage across the MR element.
MR sensors are known to be useful in reading data with a sensitivity exceeding that of inductive or other thin film sensors. However, the development of Giant Magnetoresistive (GMR) sensors (also referred as GMR head chips) greatly increased the sensitivity and the ability to read densely packed data. The GMR effect utilizes a spacer layer of a non-magnetic metal (chosen to ensure coupling between magnetic layers is weak) between two magnetic metals. GMR disk drive sensors (or head chips) operate at low magnetic fields and when the magnetic alignment of the magnetic layers is parallel the overall resistance is relatively low. When the magnetic alignment of the layers is anti-parallel, the overall resistance is relatively high. Physical stress in the sensor caused by the anti-parallel alignment increases electrical resistance and current in the GMR sensor causing the sensor to heat up. Also, heat from other components within the disk drive combine with the heat generated by the sensor to further increase temperature.
As GMR sensors allow extremely high data densities on disk drives, a stable sensor is essential to accurate read and write operations in high track density hard disk drives. It is known that temperature increases may cause the GMR sensor within the GMR element to exhibit unstable magnetic properties and efforts to reduce the temperature within the disk drive are ongoing. Cooling GMR sensors and other components within the hard disk drive increases sensitivity and improves read/write performance of the GMR sensor. Various methods of cooling hard disk drive components are known and include forced air, cooling fans, cooling fins, heat pipes, etc. Generally, the cooling methods have been limited to attaching materials or structures that have high thermal conductivities to transfer heat away from the sensor. However, due to space limitations and ambient conditions elaborate means of cooling are generally not available to the GMR sensor.
Therefore, it is desirable to provide a method for cooling GMR heads and other components in hard disk drives, that would be practical and fit within the subject structure without requiring serious structural changes to the hard disk drive. Cooling GMR head chips would significantly enhance magnetic sensing capacity of GMR head chips during the read operation and increase performance of the write operation. It would also be desirable to provide a practical method for cooling GMR heads that would allow utilization of GMR materials that have significantly higher sensitivities. Additionally, since other heat producing components within the data storage device may materially affect performance of the device's read/write sensors and it would be desirable to provide a method that would reduce heat generated by the other components.